High power feedthroughs for passing electrical and radio frequency (RF) energy through walls, bulkheads, etc., are known. Such feedthroughs typically comprise an insulative material, such as ceramic, mounted to a flange extending from the wall at a location surrounding an opening therethrough. The insulator typically supports and spaces a conductor away from the flange/wall structure by a sufficient distance to prevent arc-over. Such arrangements work well, unless a hostile environment is presented on one side of the wall, such as an extremely high pressure or vacuum contained within a hermetically sealed pressure or vacuum vessel.
As is well known to those skilled in the art, a skin effect causes most RF current to flow in the outermost region of a conductor. It is in this peripheral region of a cylindrical conductor that electronic resistance and inductive heating is also concentrated.
A prior approach to feeding RF energy at high power levels through to the interior of a high vacuum vessel was to bond a hollow RF conductor tube to an outwardly concentric ceramic insulator and then pass cooling fluid through the conductor tube in order to conduct heat generated electronically within the conductor tube away to a suitable heat exchange/dissipation apparatus. The drawback presented by this prior approach was that the ceramic-to-conductor tube bond because highly stressed due to the tremendous thermal gradient thereacross, leading directly to mechanical failure.
Thus, a hitherto unsolved need has arisen for an effective high power RF feedthrough for pressure or vacuum vessels which enables cooling fluid to flow directly adjacent to the insulator-to-conductor bond region, thereby providing requisite cooling to the bond region and extending considerably the useful life of the feedthrough.